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gary_252575
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Confusion in Diversity & Demand Factor

10/14/2010 3:50 AM

i was calculating load for a building, all of sudden i found 0.35% diversity factor used. when i discussed that problem with my senior engineer, he told me that particular equipment is used minimum. so is he right. if yes trhen please explain me in breif the diversity factor, demand factor, load factor..
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Hameedullah Ekhlas
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#1

Re: confusion in Diversity & Demand factor

10/14/2010 3:56 AM

I do not want to interfere in your discussion but let me tell you that Diversity factor is more than one and Demand factor is less than one. For more information please see this link.

http://cr4.globalspec.com/thread/58555
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nascon
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#2

Re: confusion in Diversity & Demand factor

10/14/2010 4:50 AM

Dear Friend,

Load factor is actual load with respect to rating of equipment., such as one motor rated at 100 kw with say 95% efficiency loaded maximum at 80 % , with the such various load connected , out of number of drives % of drives may be running at a time are with consideration as diversity say out of 10 drives 7 runs at a time at worked out load considering the load factor. Hence 100 x.95 x.8 = 76 kw iwth consdering load factor. Now having ten such motors i.e 10 x 76 = 760 considering diversity x.7 = 532 kw is demand load.
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TonyS
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#3

Re: confusion in Diversity & Demand factor

10/14/2010 5:52 AM

Maximum Demand and Diversity

The Wiring Regulations

BS 7671 requires that the maximum demand of an installation be assessed. The purpose of the assessment is to ensure that the supply to the installation will be of sufficient current-carrying capacity for the purpose for which the installation is intended. An assessment of maximum demand requires that sufficient information is known about how the installation is likely to be used and any diversity factors that may be applied. Diversity factors, together with knowledge of the connected load, are used to calculate the maximum demand.

Maximum demand
The maximum demand of an installation is the maximum rate of consumption expressed in amperes, kW or kVA. It is generally taken as the average rate of consumption over a period of time, usually 30 minutes but in some cases 15 minutes or even an hour, depending on the tariff and electricity meter. Maximum demand does not include motor starting currents or other transient effects. Fault currents and overload currents are also excluded. Maximum demand in KW is relevant only for metering/tariff purposes. For the design of an installation, kVA or amperes must always be used.

Diversity factor

This is a factor which takes into account the:

· time profiles of electrical loads

· coincidence of electrical loads

· mechanical loading of electric motors

· seasonal changes in loading (particularly heating, lighting and cooling)

· any special requirements for the particular installation

A diversity factor may be described as a factor expressing the maximum demand as a fraction of the connected load.

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TonyS
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#4
In reply to #3

Re: confusion in Diversity & Demand factor

10/14/2010 6:12 AM

The confusion would to me, seem to be interpretation of codes of practice.

I've always worked on diversity being equal to or less than one.
A ring main would never be permitted otherwise.

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Hameedullah Ekhlas
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#5
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Re: confusion in Diversity & Demand factor

10/14/2010 6:34 AM

Tony, Please see these links plz.

http://www.nfpa.org/assets/files/PDF/necdigest/CodeIssues072704.pdf

Please read below wikipedia it explains diversity factor per percentage.


http://en.wikipedia.org/wiki/Diversity_factor

Here I have quoted

"as distinguished from diversity factor refers to the percent of time available that a machine, piece of equipment, or facility has its maximum or nominal load or demand (a 70% diversity means that the device in question operates at its nominal or maximum load level 70% of the time that it is connected and turned on)."
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W. T. McGonagall
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#6
In reply to #5

Re: confusion in Diversity & Demand factor

10/14/2010 8:54 AM

So a ring main with say 15 – 13A socket outlets @ 70% would require a supply of 136.5A?
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PWSlack
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#15
In reply to #6

Re: confusion in Diversity & Demand factor

10/15/2010 3:36 AM

Eh? Why would it, if it is protected with a 30A fuse or a 32A MCCB?

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TonyS
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#7
In reply to #5

Re: confusion in Diversity & Demand factor

10/14/2010 9:05 AM

"A diversity factor may be described as a factor expressing the maximum demand as a fraction of the connected load".
A fraction = less than one.

So according to you BS7671 (17th edition) is wrong.
I'm sure the IEEE would like to note your views.

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msamad
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#8
In reply to #7

Re: confusion in Diversity & Demand factor

10/14/2010 9:34 AM

The difference between the demand factor and the diversity factor has been well explained in the links provided in some comments. Here are the definitions of some of the terms (including demand factor and diversity factor) related to this topic:

Demand Factor - Maximum load divided by the connected load. It is less than 1. It indicates the magnitude of maximum load compared to the connected load and is used to calculate the required capacity from the connected loads.

Diversity factor - It is the ratio of the sum of the individual non-coincident maximum demands of various subdivisions of the system to the maximum demand of the complete system.

For example, a sub-station has three outgoing feeders: feeder 1 has maximum demand 10 MW at 10:00 am, feeder 2 has maximum demand 12 MW at 7:00 pm and feeder 3 has maximum demand 15 MW at 9:00 pm, while the maximum demand of all three feeders is 33 MW at 8:00 pm. Here, the sum of the maximum demand of the individual sub-systems (feeders) is 10 + 12 + 15 = 37 MW, while the system maximum demand is 33 MW. The diversity factor is 37/33 = 1.12. The diversity factor is usually greater than 1, its value also can be 1 which indicates the maximum demand of the individual sub-system occurs simultaneously.

Loading factor - Average load divided by the peak load, over a period of time. If a 50 kw motor's average load is 40 kw, the loading factor is 0.8. It indicates how much load is applied compared to the capacity.

Duty factor - The duty factor (or 'cycle') of a motor refers to the on-time of the motor versus the total time. Duty factor 1 means continuous duty.

Peak factor (also called Crest Factor) - The ratio of the maximum value to the r.m.s value. For sine true wave, it is 1.414. It is used to indicate the systems harmonics. The more its value deviated from 1.414 (either less or greater), the more is the harmonics.

Form Factor - It is the ratio of rms value to average value. For sine wave it is = 1.11

Ripple Factor - It is the ratio of the root mean square (rms) value of the ripple voltage to the absolute value of the dc component of the output voltage, usually expressed as a percentage. It is used to indicate the quality of DC of the rectifier. The less the value, the better is the quality.

- MS

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msamad
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#10
In reply to #8

Re: confusion in Diversity & Demand factor

10/14/2010 10:04 AM

Just a quick note: The above are the terminologies used in generic, some may interpret it in different way (may use the concept of demand factor and diversity factor mixed, as appears to me happens in BS7671 – nothing wrong with this. Both of the terms eventally are used to calculate the required system capacity from the connected load.)

- MS

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TonyS
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#14
In reply to #10

Re: confusion in Diversity & Demand factor

10/14/2010 1:50 PM

I seem to recall saying that in an earlier post.

To be honest I've never liked BS7671, I was brought up with M&Q1956 (electricity). Far stricter in some ways, but also in line with practicalities.

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gary_252575
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#13
In reply to #4

Re: confusion in Diversity & Demand factor

10/14/2010 11:00 AM

the same is with me... but how could we ignore what hameed says.. coz i have gone through the links send by him. he is even correct then why there is so much deiversity...
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gary_252575
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#12
In reply to #3

Re: confusion in Diversity & Demand factor

10/14/2010 10:57 AM

tony would you help me how to evaluate the current.
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mountk2
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#9

Re: Confusion in Diversity & Demand Factor

10/14/2010 9:59 AM

When you install 8 power sockets in a single room workshop:

(a) If the Owner has only six machines to connect, will be at any of the six sockets out of eight - that is a case of diversity.

(b) If the Owner wants to practically use out of 6 any 4 machines on the average - that is a case of Load Factor.

(c) If the Owner uses say 4th machine for less than 15 minutes along with other three regulars; from the view point of power supply company - that is a case of demand factor.

Luckily the complex areas have been very well take care of by Hameedullah Ekhlas, he has made a come back after a long long time - This time with a big bang.

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kvsridhar
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#11

Re: Confusion in Diversity & Demand Factor

10/14/2010 10:07 AM

i get a feeling that the terms have different meanings in USA and IEC. For example, diversity factor as defined by IEC 60439 is as follows, always <1.

http://cr4.globalspec.com/thread/58555#comment611164

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gary_252575 (2); Hameedullah Ekhlas (2); kvsridhar (1); mountk2 (1); msamad (2); nascon (1); PWSlack (1); TonyS (4); W. T. McGonagall (1)

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